An Fe·MOF–Mo·POM hybrid material: a novel and efficient catalyst for selective benzyl alcohol oxidation to benzaldehyde

Abstract

Designing and synthesis of an efficient catalyst for the selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzCHO) is a significant method in green chemistry and catalysis. This study has focused on the preparation of a new hybrid material as a result of ion exchange between positively charged NH₂-MIL88B(Fe) (Fe·MOF) and H₃PMo₁₂O₄₀ (Mo·POM). The obtained hybrid material was characterized by various techniques, like Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), and N₂ adsorption/desorption analysis. The XRD pattern and FT-IR spectrum confirmed that the obtained hybrid material consisted of both Fe·MOF and Mo·POM. The N₂ adsorption/desorption isotherms clearly showed the decreasing surface area of Fe·MOF after modification with Mo·POM. The prepared Fe·MOF–Mo·POM was subsequently utilized as a catalyst in the selective oxidation of BzOH to BzCHO. Various solvents, oxidants, and time were considered to find the best reaction conditions. The highest conversion (87%) and selectivity (99%) were obtained in the presence of tert-butyl hydroperoxide and DMF at 8 h. The prepared catalyst is recyclable four times without loss of catalytic efficiency.